1. Field of the Invention
The present invention relates to a semiconductor device manufacturing system capable of carrying out resist stripping or surface pre-treatment of substrates by use of a gas such as chlorosulfuric acid with higher reactivity.
2. Description of the Prior Art
In recent years, in semiconductor device manufacture. a photoresist film (referred to simply as a "resist film" hereinafter) has been commonly used as a mask for ion implantation or a mask for dry etching.
In the resist film formed via such process, there has been contained an ion-implantation element such as arsenic (As), phosphorus (P), boron (B), or the like, or an inorganic element such as aluminum (Al), titanium (Ti). or the like which is used as electrode material to be patterned. As a result, a complex compound is formed as a reaction product of the above element with the material of the resist film.
Such resist film is not easily removed by the conventional resist film removing methods employing oxygen plasma, ozone, etc. and, therefore, complicated processing has been needed.
In addition, recently a resist film removing method using sulfuric anhydride (SO.sub.3) has been disclosed in "52/Semiconductor International, September 1996", "Monthly Semiconductor World 1996, 11",
However, in the resist film removing method using sulfuric anhydride (SO.sub.3), in many cases the resist film containing inorganic elements is not easily removed.
Further, in the prior art, recently a mixed solution using sulfuric acid, hydrochloric acid, ammonia, hydrogen peroxide, etc. has been employed mainly in cleaning the silicon wafer prior to film formation. Such a mixed solution is effective for removal of metal, organics, etc. and thus it can be used as an effective cleaning method.
Meanwhile, in recent years, patterns of the semiconductor have become finer, so that the opening of the trench has been made narrow and also the ratio of the depth to the opening width (this ratio is called an aspect ratio) has been increased to as large as 5 to 8.
In the case of such a deep trench having a narrow opening, in the above chemical processing, it has been difficult for the chemicals to enter into the bottom of the trench, and it has also become difficult to remove the chemicals with a pure water wash once the chemicals have entered to the bottom. Accordingly, it has become extremely difficult to completely clean the bottom and the side walls of the trench.
Further, in the case where an insulating film is formed by the CVD method to cover wirings after the surface treatment, the insulating film has been difficult to deposit on the concave portions between the wirings and thus sometimes deep hollow portions have been formed in the centers of the concave portions. As a result, another problem has developed that, when a conductive film used as the wirings is formed on the insulating film, such conductive film cannot be deposited satisfactorily on such hollow portions and such conductive film within such hollow portions cannot be removed.
For example, when chemicals such as EKC (product name, available from the EKC corporation) are employed in resist stripping, and when the film is formed by the CVD method after the conventional pre-treatment for film formation, the growth rate of the SiO.sub.2 film is extremely low on such hollow portions, so that the hollow portions are not perfectly buried. The reason for this, though not clearly analyzed, is supposed to be that EKC cannot be completely removed from the surface of the underling insulating film and remains thereon and then residual EKC exerts an unfavorable influence upon the growth rate of the SiO.sub.2 film.
Furthermore, in the case where a film is formed on the insulating film, e.g., silicon thermal oxide film on the semiconductor substrate by thermal CVD method using a reaction gas containing TEOS (tetraethylorthosilicate), there has arisen still another problem in that the rate of film formation becomes extremely low on the insulating film as compared with the case where the film is formed directly on the silicon substrate.
Moreover, the amount chemical consumption has increased more and more as the diameter of the wafer is enlarged from 200 mm to 300 mm. As a result, not only has the cost of production risen, but also it takes enormous time and labor to process the waste fluid. In addition, there is another problem of environmental protection.
In order to overcome the above problems, a technique for the surface treatment using vapor of sulfuric acid, hydrochloric acid, or chlorosulfuric acid has been proposed.
Use of a vapor enables the treatment of narrower recess portions. Since vapor, especially vapor of chlorosulfuric acid, also has very strong reactivity, the resist film stripping and the surface pre-treatment of the substrate on which the films are formed can be performed more completely.
However, the chlorosulfuric acid reacts strongly with water to generate sulfuric acid and hydrochloric acid by hydrolysis. Hence, if the chlorosulfuric acid reacts with moisture in transport of the process gas, to generate sulfuric acid and hydrochloric acid, chlorosulfuric acid at a predetermined concentration cannot be introduced into the process chamber, so that there is a possibility that the desired process cannot be performed.
In addition, if such acid adheres to the surface of the substrate, unevenness is caused in processing. Therefore, after the process using the vapor of chlorosulfuric acid, etc. has been conducted, residue of the chlorosulfuric acid, the sulfuric acid and the hydrochloric acid must be removed by cleaning the inside of the process chamber prior to a succeeding process.
Because the vapor of the chlorosulfuric acid, etc. is difficult to handle, the existing state of the process using vapor of chlorosulfuric acid, etc. is at an experimental level. An apparatus which is suitable for mass production using vapor of chlorosulfuric acid, etc. has not yet been developed.